The present invention relates generally to optical fibers and, more specifically, to the testing of skew in optical fibers.
Data, such as Voice Data, Image Data or the like are typically handled using computers that transfer the relevant information in a digitized form through electric cables, fiber optic cables, radio frequency transmission or the like. Increasing demand for digitally transferred information has driven research in the area of fiber optics. Throughput of digital data in optical fibers depends on the speed of the signal, the number of signals that can be simultaneously transferred using different wavelengths (i.e., the bandwidth), and the frequency of the individual signals. Since optical fibers use light pulses to form digital signals, the signal speed is already at a maximum (i.e., the speed of light). While the transmission of multiple simultaneous signals having different wavelengths through a single optical fiber is possible, the high cost of light emitters capable of sending out such signals currently makes this approach uneconomical. Accordingly, digital data throughput in optical fibers has been increased by increasing the frequency of individual signals.
However, as signal frequency increases, errors caused by the skew in fiber optic cables has become a concern. In fiber optic cables including at least two optical fibers, differences in light transmission times between individual optical fibers, also referred to as skew, can occur. For computers having sufficiently fast processing speeds, skew can result in errors in the interpretation of transmitted digital data.
In an attempt to prevent excessive skew in fiber optic cables, it is common to select individual optical fibers having a desired light transmission time and to bundle the appropriate optical fibers together to form a fiber optic cable. Unfortunately, this method of forming fiber optic cables has the drawback that skew can be introduced into the fiber optic cable during the process of assembling the individual optical fibers into a fiber optic cable. Thus, even when starting with individual optical fibers having acceptable light transmission times, the resulting fiber optic cable can have excessive skew, i.e., can have optical fibers which exhibit too great a difference in their respective light transmission times. Another drawback is the manufacturing inefficiency resulting from having to select each individual optical fiber for use in a single fiber optic cable prior to assembling the fiber optic cable.
What is needed, but is not provided by the conventional art, is a method of testing and adjusting the skew of a fiber optic cable, or a group of optical fibers, that allows greater manufacturing efficiency when producing fiber optic cables.
Briefly stated, one embodiment of the present invention is directed to a method of testing optical fibers. The method includes: providing at least two optical fibers; transmitting a light at a first end of the at least two optical fibers; measuring a light transmission time for each of the at least two optical fibers; determining a difference in the light transmission times for the at least two optical fibers; determining whether the difference in light transmission times is above a predetermined value; and if the difference in the light transmission times is above the predetermined value, adjusting an amount of optical material forming at least one of the at least two optical fibers to reduce the difference in the light transmission times.
Another embodiment of the present invention is directed to a method of testing a fiber optic cable. The method includes: providing a fiber optic cable having a first and second end, the fiber optic cable including at least two optical fibers; transmitting light at the first end of the fiber optic cable; measuring the light transmission time for the light to travel through each of the at least two optical fibers of the fiber optic cable; determining the difference in the light transmission times for the at least two optical fibers of the fiber optic cable; and determining whether the difference in the light transmission times is above a predetermined value.